In elevator systems, suspension and transmission ropes are used for supporting and/or moving an elevator car, a counterweight or both. Elevator ropes are generally made by braiding from metallic wires or filaments and have a substantially round cross-sectional shape. A problem with metallic ropes is, due to the material properties of metal, that they have high weight and large thickness in relation to their tensile stiffness and tensile strength.
Also light-weight suspension and transmission ropes, where the width of the rope for a hoisting machine is larger than its thickness in a transverse direction of the rope, are known. The rope comprises a load-bearing part made of composite materials, which composite materials comprise non-metallic reinforcing fibers in polymer matrix material. The structure and choice of material make it possible to achieve low-weight suspension and/or transmission ropes having a thin construction in the bending direction, a good tensile stiffness and tensile strength. In addition, the rope structure remains substantially unchanged at bending, which contributes towards a long service life.
Several mechanical and electrical methods have been presented to provide a tool for condition monitoring of elevator suspension and transmission ropes. For instance, a method for monitoring condition of steel strands wound into a cord and encased in a jacket within a belt in an elevator system is known from prior art. The development of non-destructive controls allowing damage detection in fibre-reinforced polymers during service life is a key problem in many practical applications also in elevator technology. Many of these non-destructive tests involve the periodic inspection of composite components by means of costly equipment. Furthermore, the problem in using testing of electrical properties of the rope is that the initial values vary in each rope and might be different after installation ropes in the elevator. There is thus a growing need for cost effective and reliable condition monitoring methods of elevator ropes which integrate sensors allowing the in situ monitoring of damage throughout the elevator life.